1. Field of the Invention
This invention relates to automatic wire-laying apparatus and, more particularly, to the wiring heads employed in an automatic cable harness forming machine.
2. Description of the Prior Art
Until the recent development of automatic cable harness forming machines, such harnesses, employed extensively in many complex electronic systems, such as telephone switching equipment, PBX's, and computers, to mention but a few, were almost exclusively formed manually. This entailed laying out the various colored (or otherwise coded) wires on wiring boards having an array of pins supported and arranged thereon in accordance with a pattern corresponding to a set of written instructions for a particular cable harness. Such a procedure is obviously time consuming, tedious and expensive.
In an attempt to speed up the manual operations in forming a cable harness and, particularly, the laying out of the wires to form a patterned array, a number of visual and audio systems have been proposed and/or used heretofore. These systems, for example, have employed television monitors and/or speakers, or earphones, to provide the assembler with step-by-step wiring instructions. A related system is disclosed in U.S. Pat. No. 3,163,296, of E. W. Gray, wherein indicating lamps adjacent the wiring pins are selectively operated to indicate to the assembler the particular route that a given wire is to follow. Regardless how the wires are laid out along the various prescribed paths between selected pins, they are, of course, thereafter bound, cut and the ends thereof selectively stripped of insulation to form the finished cable.
While these latter approaches to forming cable harnesses have proved to be of considerable assistance to the assembler, it was not until the advent of automated cable forming machines that the time and costs involved in forming complex cable harnesses were substantially reduced. One such machine with which the present invention is primarily concerned, is disclosed in B. H. Hobbs et al U.S. Pat. No. 3,907,007, issued Sept. 23, 1975, and assigned to the same assignee as the present invention.
In that cable forming machine, the wires are automatically laid out on a wire-receiving board or frame, typically in accordance with a programmed X-Y coordinate pattern. The machine includes a bank of wiring heads, one for each wire or set of wires, and through which the wires extend from respective tensioning devices and supply reels. The wiring heads are releasably attached to respective seats, and selectively coupled to a wire positioning device mounted for movement in accordance with an X-Y coordinate wiring pattern, with periodic displacement in the Z direction.
Each of the wiring heads in one prior embodiment of the above-described machine has included a resiliently mounted, and downwardly extending wire guide tube. As constructed, the prior guide tube mounting assembly allowed the guide tube to "pop-out" upon hitting an obstruction, such as a slightly bent pin or an abnormally raised wire. This, in turn, actuated a pair of orthogonally positioned switches to turn off the machine. Disadvantageously, whenever a given guide tube would "pop-out" of the wiring head, it could only be remounted by partially dismantling the wiring head. Having to remount the guide tube, even infrequently, has proved to be not only time consuming, but costly, because of the necessary down-time of the machine.